In the operation of various types of machinery or equipment, it is frequently necessary to provide a drive system having an output shaft which is capable of being quickly started and stopped, or quickly reversed or driven in the same direction at a different speed. For some machinery, a drive system including an electrically actuated clutch and brake unit is adequate, especially when the horsepower requirements are relatively low. However, with other machinery requiring relatively higher horsepower drive systems, it has been found desirable to use one or more oil shear clutch-brake units of the general type, for example, as disclosed in U.S. Pat. No. 3,638,773 and No. 3,924,715 which issued to the assignee of the present invention. The construction and operation of these clutch-brake units are described in the patents and provide for quickly starting and stopping an output shaft with respect to an axially aligned and continuously driven input shaft. Each unit has a series of interfitting clutch plates and discs and a series of interfitting brake plates and discs. Oil is recirculated within the housing between the plates and discs to provide for cooling and lubricating the plates and discs and thereby significantly extending the useful service life of the clutch-brake unit.